1. Field of the Invention
The present invention generally relates to a gas injector and a cover plate assembly applied in a semiconductor equipment, and more particularly to a temperature-controllable cover plate assembly and a detachable gas injector thereon.
2. Description of the Related Art
In thin film deposition process, the temperature of the lower surface of a ceiling attached on a cover plate must be controlled at about 300° C. in order to avoid the accumulation of particles on the lower surface of the ceiling and the subsequently dropping of the particles on a wafer in manufacturing process and poor yield ratio of production. The temperature of the lower surface of the ceiling depends on the combination arrangement and cooling methods between the cover plate and the ceiling.
In the thin film growth process, reaction gases are horizontally injected above a susceptor by a gas injector to be mixed, and films are then deposited on a wafer through physical or chemical reactions induced by heating. The injector is designed to horizontally inject the reaction gases and render the reaction gases uniformly distributed on the surface of the rotating susceptor so as to form a uniform boundary layer on the surface of the susceptor to facilitate the deposition of thin films. In addition, the spacing and angle of injector outlets also have a decisive influence on process result.
Conventional cover plate is a single-layer structure with direct water cooling. A space is between a ceiling attached on the cover plate and the cover plate for introducing a gas mixture of gases with different flow rate to control the temperature of the lower surface of the ceiling in order to prevent accumulation of particles in the process attached to the lower surface of the ceiling and the subsequently dropping of the particles on a wafer in manufacturing process so as to degrade yield ratio of production. This design must use hydrogen (H2), nitrogen (N2) and the mass flow controller (MFC) to adjust different gas combinations and different flow rates of gas, and uniformly maintain the distance between the ceiling and the cover plate at 0.1 mm, to facilitate flow uniformity of the gas combination and to achieve uniformity of temperature.
Conventional injectors horizontally inject reaction gases above a susceptor in a chamber in a thin film growth process, the gases mix and deposit on a substrate to form a thin film through physical or chemical reactions induced by heating. One-piece injector is formed by combining multiple components via brazing with disadvantages of lower yield rate and easy leakage of cooling water due to cloggy narrow fluid conduit rendering it necessary to replace the entire injector. Moreover, the pitch between outlets of the injector is fixed unable to be adjusted which will limit the adjustments of parameters such as flow speeds and flow field/distribution. The whole injector must be replaced in order to change flow speeds and flow field.
Therefore the invention provides a gas injector and cover plate assembly to prevent the accumulation of particles attached on the lower surface of a ceiling in the process, and to improve the production yield ratio, along with characteristics of adjustable flow velocities and flow field/distribution, and to facilitate the process development.